The present invention relates generally to the preparation of semiconductor devices and more particularly to improved slurry compositions for the chemical-mechanical planarization (CMP) of metal (e.g., Cu) layers and barrier materials (e.g., Ta, TaN, etc.) and dielectric materials for their polishing.
A semiconductor wafer typically includes a substrate, such as a silicon wafer, on which a plurality of integrated circuits have been formed. In the manufacture of integrated circuits, wafer surface planarity and quality is of extreme importance. In order to achieve the degree of planarity required to produce ultra high density integrated circuits, CMP processes are being employed.
In general, CMP involves pressing a semiconductor wafer against a moving polishing surface that is wetted with a chemically reactive, abrasive slurry. Conventional slurries either are acidic or basic, and generally contain alumina, silica, zirconium oxide, magnesium oxide, or cerium oxide abrasive particles. The polishing surface usually is a planar pad made of a relative soft, porous material, such as polyurethane. The pad usually is mounted on a planar platen. Continuous pad devises also are being tested. Systems devoid of a slurry where the pad contains the abrasive also are being used.
Integrated circuits are chemically and physically integrated into a substrate by patterning regions in the substrate and layers on the substrate. The layers generally are formed of various materials having either a conductive, insulating, or semiconducting nature. Also, barrier materials or barriers are used to prevent the migration of ions and adhesion promoters. In order for a device to have high yields, it is crucial to start with a flat semiconductor wafer. If the surface is not uniform (e.g., areas of unequal elevation or surface imperfections), various problems can occur which may result in a large number of inoperable devices. Further in this regard can be found in the following references: Luo, et al., "Chemical-Mechanical Polishing of Copper: A Comparative Analysis," February 13-14 CMP-MIC Conference, 1997 ISMIC--200:197/0083; Babu, et al., "Some Fundamental and Technological Aspects of Chemical-Mechanical Polishing of Copper Films: A Brief Review," February 19-20, 1998 CMP-MIC Conference, 1998 IMIC--300P98/0385; Tseng, et al., "Effects of mechanical characteristics on the chemical-mechanical polishing of dielectric thin films," Thin Solid Films, 290-291 (1996) 458-463; Nanz, et al., "Modeling of Chemical-Mechanical Polishing: A Review," IEEE Transactions on Semiconductor Manufacturing, Vol. 8, No. 4, November 1995; Stiegerwald, et al., "Pattern Geometry Effects in the Chemical-Mechanical Polishing of Inlaid Copper Structures,": "J. Electrom. Soc., Vol 141, No. Oct. 10, 1994; Fury, "Emerging developments in CMP for semiconductor planarization--Part 2," Solid State Technology, 81-88, July 1995; Fury, "CMP Standards: A Frustration Cure," Semiconductor International, November 1995.
A related, but different, operation performed on magnetic disks is called "texturing." Texturing is used to reduce stiction (static friction). More irregular surfaces have lower stiction and this leads to the practice of texturing disk surfaces using fixed or free abrasive particles. Texturing operations are known in the art to utilize typically &lt;0.4 .mu. diamond at a concentration of less than 2 carats/liter in order to achieve approximately 7A Ra by AFM. Alumina also is a common abrasive used in texturing operations. See for following references in this regard: Cooper, et al., "Tapes for Polishing and Texturing Thin-Film Magnetic Disks," Technical Information Report presented at Discon USA '96, Texwipe Company LLC; and Bhushan, "Magnetic Slider/Rigid Disk Substrate Materials and Disk Texturing Techniques--Status and Future Outlook," Adv. Info. Storage Syst., Vol. 5,1993: 175-209.
Despite CMP being commercially practice, there still are a number of problems including, for example, non-uniformity in material removal rate, Cu dishing, oxide erosion, Cu line corrosion, and other surface defects. Thus, there exists a need in CMP for improvements.